In Accordance with Wilson and MacArthur's Theory of Island Biogeography

In accordance with Wilson and MacArthur's theory of island biogeography, the following equations represent the immigration and extinction rates of species of beetles on a small island. (I = immigration rate of species per month; E = extinction rate of species per month; S = number of species currently on the island.)
I = 9 ? 0.2S
E = 0.3S
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If there are 25 species on the island, the expected immigration rate is _______ species per month and the expected extinction rate is _______ species per month.

A) 1; 7.5
B) 4; 7.5
C) 7.5; 1
D) 7.5; 4